High-speed rail vehicles are generally provided with a high voltage equipment box, high voltage of 25 KV coming from a pantograph passes through a vacuum circuit breaker in the high voltage equipment box and then enters into a traction transformer. Currently, the minimum clearance for equipments in the high voltage equipment box, such as the vacuum circuit breaker, is about 230 mm, which only meets the requirement of overvoltage level OV3 (GB/T21413.1), and does not meet the requirement of overvoltage level OV4 (GB/T21413.1).
For vehicles running at high altitudes, due to decreased air pressure or air density, the external insulation strength of the vehicles is reduced accordingly, and the external insulation withstand voltages of the electric components need to be modified, and the clearance for electric equipments is required to be increased accordingly. Also, high altitude regions has relatively fierce sand wind and low temperature, the vehicles running at high altitudes are further required to have capabilities of withstanding wind pressure and low temperature.